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Taxonomic information across the Internet

Key to main Polychaete families

This key deals with only the main benthic families.

Many of the questions are link to images which illustrate the features being sought. The images will appear on the right hand frame. In turn many of these images are specific to particular families. If you recognise an image as being similar to a feature on your worm you can often click on the image and it will take you to the relevant family. So there are a number of ways of trying to identify your worm.

Please answer as many questions as possible, then press Analyse.

The key construction is quite a simple program and relies on you answering as many questions as possible. Occasionally you will get some results which may seem strange so please use the hyperlinks to browse through the families given in the answer to see which one seems closest to your specimen.


1 Body divided into clearly defined regions. Not gradually changing down the body
2 Dorsal segmentation hidden by scales or rows of setae
3 Body quadrangular in cross section
4 Body dorso-ventrally flattened. Not cylindrical
5 Operculum
6 Posterior end covered by a hard chitinous shield
7 Segments distinctly longer than wide
8 Ventral furrow present
9 Dorsal surface with rows of spherical tubercles
10 Calcareous tube
11 Proventriculous (Barrel shaped organ in anterior gut)
12 Jaws
13 Prostomium without appendages
14 Head with appendages
15 Caruncle
16 Palps
17 Branchiae
18 Branchial position
19 Parapodia
20 Dorsal cirri
21 Simple Setae
22 Simple hooks
23 Hooks with toothed apex
24 Uncini
25 Lyrate, Furcate or forked setae
26 Compound setae